Impact of smoking on outcomes in patients with Myocardial Infarction with Non-Obstructive Coronary Arteries — an observational study

BACKGROUND: The pathomechanism of myocardial infarction with non-obstructive coronary arteries (MINOCA) is diverse and not fully explained. One of the factors for cardiovascular risk evaluation is smoking. Nevertheless, "smoker's paradox" is a controversial phenomenon in patients with myocardial infarction, which can imply better outcomes in smokers than non-smokers. AIMS: This study aimed to assess the association between smoking and clinical outcomes in MINOCA patients. METHODS: In this study 6045 patients hospitalized with a working diagnosis of MINOCA were evaluated, of whom 4808 (79.5%) were non-smokers. Our analysis included baseline characteristics, outcomes, and readmission rates during a 36‑month follow‑up. RESULTS: Smoking patients were significantly younger (59 [52-66] vs. 70 [60-78] years; P <0.001) than non-smokers. There were more male patients in the smoking (64.92% vs. 40.95%) than in the non-smoking group. Smokers were less likely to have traditional risk factors, more frequently had symptoms of angina (89.29% vs. 86.87%; P = 0.03), and had lower mortality during hospitalization (0.81% vs. 1.75%; P = 0.02), after 12 months (8.08% vs. 11.69%; P <0.001) and after 36 months (13.34% vs. 16.95%; P = 0.002), as compared with non-smokers. Nevertheless, multivariable analysis showed that smoking was one of the independent risk factors for 36‑month mortality (hazard ratio, 1.23;95% confidence interval, 1.03-1.47; P = 0.02). CONCLUSIONS: This study showed that lower 36‑month crude rates of death among smokers (comparing to non-smokers) may be explained by a significantly lower burden of traditional risk factors and the younger age of smokers. After adjusting for baseline differences, tobacco use remained an independent risk factor for 36‑month mortality.